Lubricating grease compositions inhibited against oxidation



Sept. 27, 1960 B. w. HOTTEN LUBRICATING GREASE COMPOSITIONS INHIBITEDAGAINST OXIDATION Filed June 13, 1956 00 0 8WM7MWNM a vi w t so 00 /20#0 m 7/! M/ l/Ol/IJ AQA . INVENTOR. ail/Ci 14 #0775 BY. Q KAN).

United States Patent "f" LUBRICATING GREASE COMPOSITIONS INHIBITEDAGAINST OXIDATION Bruce W. Hotten, Orinda, Califi, assignor toCalifornia Research Corporation, San Francisco, Calif., a corporation ofDelaware Filed June 13, 1956, Ser. No. 591,049

7 Claims. (Cl. 252-32) This invention relates to lubricatingoilcompositions, more particularly to greases. More specifically theinvention relates to the inhibition of oxidation of lubricants, e.g.,greases, at high temperatures, and to oxidation inhibitors effective forhigh temperature lubrication.

Modern usage and increasingly severe requirements necessitate, amongother things, the use of oxidation inhibitors for lubricating oilcompositions, for example, greases, which are capable of performance athigh temperatures. Many inhibitors are available, e.g., tert. butylphenols and hydroquinone, which are efiective as oxidation inhibitorsbut which are volatile and evaporate from lubricating oil compositionsat high temperature.

It is an object of the present invention to provide new compounds whichare efiective for inhibiting oxidation of lubricants, particularlygreases, at high temperatures.

It is another object of the invention to provide lubricants,particularly greases, which are stable against oxidation at hightemperatures.

It is a further object of the invention to inhibit the oxidation of hightemperature greases with inhibitors which have a low volatility.

These and other objects of the invention will be ap parent from theensuing description and the appended claims.

In accordance with the present invention certain amides ofethylenediaminetetra-acetic acid, and/ or certain homologues, areemployed as oxidation inhibitors for lubricating oil compositions,particularly for greases. This class of compounds has been found to behighly effective for the purpose and the compounds have a desirably lowvolatility.

The inhibitors of the invention have the following type formula:

In the above type formula, R is an alkylene radical con taining two orthree carbon atoms (i.e., ethylene, tn"- methylene, propylene radicals);R R R and R are alkylene radicals containing one or two carbon "atoms(i.e., methylene, ethylene and ethylidene radicals); R R and R aresaturated or unsaturated hydrocarbon radicals containing from 12 to 22carbon atoms, e.g., aliphatic radicals containing 12 to 22 carbon atoms;and R represents hydrogen, an ester radical or a metal.

That is, in the type formula above, R may be CH .CH OI CH2.CH2.CH2-, 01'--CH2.CH

(IE3 and R R R and R may be CH or CH .CH or --CHz.CH-

CH3 The following specific examples will serve further to illustrate thepractice and advantages of the invention: Example 1.-50 gramsethylenediaminetetra-acetic acid and 156 grams of octadecylamine werereacted 2,954,342 V Patented Sept. 27, 1960 ICC by mixing and heatingthereactants to 400 F. until reaction which,

evolution of water had ceased. The occurred was as follows:

CHLCOOH HO 0 0.055 g N.CH2.CH2.OH2.N +3C1aHa1NH2+ 7 HOOC.CH2 V CHLCOOHC1sH 7NH.C 0.0112

The crude product was recrystallized from ethyl alcohol to yield a creamcolored solid melting at 90-96 F. Analysis'proved that only three of thecarboxyls of ethylenediaminetetra-acetic acid reacted. Apparentlysteric' hindrance or some other factor renders the fourth carboxyldifi'icult to react with the amine.

The octadecylamine used herein was a commercial preparation known asArmeen HT, sold by the Armour Company, Chicago, Illinois, and containing25% .hexa-' decylamine, octadecylamine, and 5% octadecenylamine.otf'this mixture consists of n-primary amines.

Example 2.-Five grams of the recrystallized product of Example 1 wereincorporated in grams of a grease comprising approximately 88 parts byweight of a solvent refined California parafiin base oil having aviscosity of 480 SSU/ 100, the oil being thickened with 12% by weight oflithium stearate. not of Example 1) was incorporated by warming thegrease to 200 F. and stirring in the inhibitor with a spatula. Theinhibitor dispersed readily in the grease to form a stable dispersion.

The base grease (no inhibitor) and the same grease; compounded with theproduct of Example 1 as described above, were subjected to ASTM D942-50Oxidation Test.

Results of the test are set forth in the graph illustrated in'theaccompanying drawing in which abscissae represents time in hours andordinates represent oxygen pressure in pounds per square inch. The testwas carried out at the standard temperature of 210 F. The initialpressure in both cases was approximately 108 psi.

It will be noted that in hours the pressuredropped.

only 7 lbs. in the case of the inhibited-grease whereas in the sameperiod of time in the case of the base grease the pressure dropped 81lbs.

The specificjinhibitor prepared as described in Example 1 and'employedand tested as described in Example 2 and in the accompanying drawing, isderived from ethylenediamine, acetic acid and octadecylamine. apparentfrom the above teachings that the alkylenediamine, the carboxylic acidand the aliphatic amine may be variedwithin suitable limits. Examples ofsuitable alkylenediamines, carboxylic acids and aliphatic amines whichmay be employed as components of the inhibitors of the invention are.settforth in the table below:

1 In compounds of the invention, the amino nitrogen may be attached tothe alpha or the beta carbon atom.

The added inhibitor (prod It will be Referring to the table and to thetype formula hereabove, R may be derived from any of the diamin e'slisted in the left-hand column; R R R and R may be derived ree any mh enb l a isis 411 12 midd 8911111911.; and R and R and R maybe defi vfrorr i-lafiy ofthe ariiines listed in the right han'd When R5 or theabove formula is an ester radical, such'ester'radic'al may be derivedfrom nionohydric alcohols having from'l to 6 carbon atoms; for example,methanol, ethanol, and normal and branched chain propanols, butanols,hexanols, etc. I

When R is a metal, such a metal can be an alkali metal or'afi alkalineearth metal; for example, sodium, potassium, lithium, barium, calciumand strontium.

Specific examples are as follows:

Trioctadec ylarnide' f ethylene'diantiiietetra-acetic' acidTrjidodec'yl-amide of ethylenediamifietetra acetic acid Trieie'osylamideof ethylenedian'iifletetraheetic' acid Trilrexadecylamide'ofethylenediaminetetra-acetic acid Trioctadecylamide oftrimethylen'edi'aminetetralacetic acid Tridodecylamideoftrimethylenediaminetetra acetie acid Trieico'sylamide ofethylenediaminefetrapropidnic 'acid(oc) Tridodecylafni'de ofethylenediamine't'etrapropionic acid(}3) Also esters and saltsef thepave;1.e.,'aerivaaveih which R is methyl, ethyl, propyL'etc. or sodium,potassium, lithium, barium, etc. may be employed.

The inhibitors of 'thefinvention are-11 5611 1n greases in sni allamount' generally between 3156111 29 arid by wighgpreferably about 2 to6% by weightbas'ed on the finis'hed grease. However, when suchinhibitors are used ili'un thickene'd lubricating oils, amounts as lowas 0.1% by weight may be used. v r

The inhibitors of theinv'ention may be used in various types oflubricants, including-lubricating oils and thickened lubricating oilssuch as greases: They are preferab ly used in greases. Representativeoils are petroleum lubricating oils (na'phthe'nic, pa'r'aifi nic mixedbase oils');' alkylene oxide polymers such as polypropylene oxidepolymers; di-este'rs such as diisdaniyl adipaf, di-2- ethylhexylaz'elat'e and di-2-ethylhexyl 'ad'ipat'e, etc.

Where the 'oils are thickened 'to'foirit grease, fli' thickeii rs maybear various types, efg.: cenventional soap type thickeners such assodium,"litl1'iu'm and calcium stearate's'; salts of dibasicacid-'diamine condensation products such as the product of condensing amolar excssof adipic acid with hexarnethylene' diatn'ine, paitia'lly"neutralizing the terminal carboxyls with n-decylar'n'ine, then formingthe lithium or sodium salt (see Dixon application Serial No. 305,287,entitled Polyamide Polyalfii'a'te' Thicken'ed Greases, filed August 19,H52, 'nOW Patent No. 2,752,312); salts of monoamid'es of tefephtlial'ic''acid of the type formula Mo 0 0 0 0.NH.R

wherein R is a long chain aliphatic groupfsuchas tetradecyl, hexa'decylor oct'ade'cyl ai'id Mjis the hydrogen equivalent of a metal, e.g.,sodiur'r} 1- lithium; and mixtures of 'arnicacid salts such as lithiumhexadecyl adipamate and dibasic acid salts such as lithium adipamate(see Dixon Serial No. 305,288, Amate-Dicarboxylate- Thickened Grease,filed August 19, 1952, now US. Patent No. 2,756,213).

Preferably the inhibitors of the present invention are 4,; employed inhigh temperature greases, by which is meant greases having dropping6111503 the ASTM US 6642 method not less than about 350 F. and whichremain unctuous and do not become hard or brittle at 350 F.

perawre a iexbe -5 bility and th'eii effectiveness arm-g0 term I claim;I r I .lt eacb ifi' ant ing viscosity thickened to the consistency anorganic grease thickening agent and having incorporated therein in airar'itduiit sufii'cinttoifihiliit'bxidation, a trialkylamide of analkylenediaminetetpaacetic acid.

2. A lubricating grease consisting essentially of a grease compositionthickened with an organic grease rpoi-ate'd therein fro Y aim gran. lrlenewherein R is an alkylene radical containing ijrorn 24913 carbonatoms, 1. 2, 3 and R4103 lky ene-radicals. containing m 1 t 2 c r pn aom @0938; R6 and R7 are hydrocarbon radicals containing from 12 to 22carbon atoms.

5 The a e. ,comn it mt ..9 ...t aim. M 51 2 th grease thickening emis ain ta a iz fia i se qaqiq-s Th e e com tiqnnte aimAw a o of lubricatingviscosity is a petroleumoil;

h se evi iwsifi n. Ri k e flit 3 a 4 a am hyle qeq fi 3 1 3 3. t yaliphatic radicals containing from 12 to 22 carbon atoms.

References Cited the tile or this btehtlf STATES PATENTS' 1,534,525Hartman et'aIJi... Apr. 21, 1925 2,191,738 Balle Feb. 27, 1940 2,347,494Meigs Apr. 25, 1944, 2,357,283 Peters sappy 5, 194g 2 ,74 V uly ,11719,11, ,978 Beeswaah ari 1 2,640,812 Bry nt' 1 In 2395;; 2,680,094Baitlet't et' a1. e 1,1954 2,700,612 chancel: 25,1955 2,780,598 c rc s'w 2,805,203 Knapper at;

OTHER REFERENCES Sequestrene, Geigyindustrial Chemicals (1952).

1. A GREASE COMPOSITION ESSENTIALLY OF AN OIL OF LUBRICATING ISCOSITYTHICKENED TO THE CONSISTENCY OF A GREASE BY AN ORGANIC GREASE THICKENINGAGENT AND HAVING INCORPORATE THEREIN IN AN AMOUNT SUFFICIENT TO INHIBITOXIDATION, A TRIALKYLAMIDE OF AN ALKYLENEDIAMINE TETRACETIC ACID.